1. Field of the Invention
This invention relates to a tobacco band apparatus incorporated in a cigarette manufacturing machine, and more particularly, to a tobacco band apparatus having a tobacco band capable of high-speed travel.
2. Description of the Related Art
A cigarette manufacturing machine generally comprises a tobacco band apparatus, a wrapping section, and a cutting section. The tobacco band apparatus has an endless tobacco band to which shredded tobacco is attracted by suction in the form of a layer. More specifically, the tobacco band is passed round a head pulley located close to the wrapping section and a tail pulley located close to a chimney for feeding shredded tobacco toward the tobacco band. The tobacco band travels in one direction as the head pulley rotates.
As the tobacco band travels, the shredded tobacco layer formed on the tobacco band is transported toward the wrapping section where the shredded tobacco is fed onto paper from a paper web. The paper from the web is caused to travel at a fixed speed in the wrapping section, and in this process of travel, the shredded tobacco is wrapped in the paper to thereby continuously form a cigarette rod. The cigarette rod thus formed is supplied from the wrapping section to the cutting section, and is cut into cigarettes with a predetermined length in the cutting section.
In order to improve the productivity of cigarettes, first of all, the speed of feeding shredded tobacco onto the paper, that is, the traveling speed of the tobacco band, need be increased. Since, however, the tobacco band is driven by rotation of the head pulley alone, as mentioned above, there occurs a large difference between the tensile force acting on a portion of the tobacco band passing around the head pulley and the tensile force acting on the other portion of the tobacco band. The difference of tension increases with the traveling speed of the tobacco band, that is, with the peripheral speed of the head pulley.
If the tension of the tobacco band is not uniform along the longitudinal direction thereof, the tobacco band is liable to slacken. Slackening of the tobacco band leads to a shorter service life and unstable attraction of the shredded tobacco to the tobacco band. As a result, the amount of shredded tobacco fed from the tobacco band onto the paper cannot be controlled uniformly.